This invention relates to the field of electromagnetic door security systems. More specifically, this invention relates to an armature adapted for attractive engagement to an electromagnet of a multiple electromagnetic lock door security system.
Electromagnetic door security systems are well-known for controlling access to secured areas. These door security systems have proven to be safe and reliable in securing a door and also allowing fail safe egress in an emergency situation. Electromagnetic door security systems typically employ a single electromagnet fixed to the door frame and a single armature mounted to the door for attractive engagement to the electromagnet. The attractive engagement generates a substantial magnetic locking force to resist opening of the door.
Electromagnetic door security systems have proven to be generally resistant to forced entry. In particular, these systems are resistant to large static forces applied to the door. However, in some operational environments and under certain extreme conditions, the bonding engagement of the single armature and the single electromagnet may be susceptible to unauthorized destruction. More specifically, it has been found in some public environments having secured gates and fire doors, unauthorized personnel can generate momentary high dynamic peak forces against the secured gates and doors. These high peak forces may be sufficient to overcome the attractive engagement of the single electromagnet and armature, and therefore defeat the door security system. Such momentary peak forces are typically generated by forceful kicks or other methods of battering against the door or gate.
These brief, but high intensity, peak forces or spikes can momentarily overcome the attractive engagement of the single armature to the single electromagnet and therefore allow the door to swing open. The problem can be particularly exacerbated by the solid doors and heavy gates typically employed in public facilities. These solid doors and gates are rigid and thus exhibit little flexion, and consequently, a substantial portion of the peak force from a kick or battering is efficiently transmitted to the door security system. In addition, the door structure may warp or deform as a result of the exerted force.
To overcome the potential deficiencies in conventional electromagnetic lock security systems, multiple electromagnetic locks have been employed to increase the locking force on a particular door.
These multiple electromagnetic lock systems theoretically provide at least twice the locking force of the single electromagnetic lock in a conventional door security system. However, multiple electromagnetic lock systems can exhibit several operational deficiencies. Typically, multiple electromagnetic lock systems employ a pair of electromagnetic locks. Each electromagnetic lock has an electromagnet and an associated armature assembly. In order to obtain maximum benefit of a multiple electromagnetic lock system, additional careful attention must be directed to providing proper alignment of the electromagnets and armatures during the initial installation procedure. Slight variations in positioning during the installation of the multiple electromagnetic locks can result in only one of the electromagnetic locks fully engaging in surface-to-surface contact when the door is in the locked state. A gap may exist between the second electromagnet and associated armature assembly even when the door is in the locked state. A significant gap between the second electromagnet and associated armature assembly may substantially decrease the bonding force of that second electromagnetic lock and therefore of the entire multiple electromagnetic lock door security system.
Warped, twisted or otherwise damaged doors can also result in only one of the electromagnetic locks fully engaging, thereby decreasing the overall bonding force of the multiple electromagnetic lock door security system. Furthermore, due to the rough use that many of these doors and gates can experience during their operational lifetime, a door can later exhibit warping, twisting and other damage that prevents full engagement of both pairs of electromagnets and armatures--even if the electromagnetic locks are initially installed correctly. Therefore, the electromagnets and armatures may require continual realignment in order to obtain the maximum bonding force of the multiple electromagnetic lock system. This requirement for continuing maintenance increases the operating costs of such door security systems.
While the invention is described as employed with a door in the following description, it should be readily understood the invention is compatible with all forms of barriers selectively positionable across openings to prevent access. This particularly includes gates and other barriers typically employed at public facilities such as subways and trains.